Drive systems for an object which is movable to and fro between to end positions are known and are preferably associated with electric motor drives. One example of an object movable in the above-described manner is a door leaf that can be moved between its open and closed positions.
From document EP 0 280 854 it is known to realize such a control system where the position detection in the end positions is not definite, but where a reference point within the door leaf travel is taken as a parameter to determine the actual door leaf position from comparing the reference point with a stored pulse number that reproducing the end positions of the object. This is aided by counting pulses from an increment detector associated with the door leaf drive motor. The positions are input in a memory on the installation of the door leaf. Because of the traversing of the reference point, continual checking takes place of the actual state of the door leaf movement, so that a correction is possible for the set value position in the course of each phase of the travel.
According to an embodiment of the above-mentioned patent, monitoring of the movement of a door leaf in both moving directions takes place on the basis of the location of the reference point between the end positions of the door leaf.